Rotor



- July 5, 1949.'

M. E. GLUHAREFF ROTOR Filed Feb. 2, 1945' MICHAEL GLUHAREFF INVENTORPatented July 5, 1949 ROTOR Michael ErGluhareff, Stratford, Conn.,assignor to United Aircraft Corporation, East Hartford, Conn., acorporation of Delaware Application February 2, 1945, Serial No. 575,896

' 16 Claims. (Cl. I'm-160.26)

The present invention relates to helicopters, and more particularly torotor blades for sustaining and/or propelling such aircraft.

Specifically, my invention comprises an improved single bladedsustaining rotor including static and dynamic counterbalancing means forcompensating the effects of drag upon the rotor, and the mass thereof.

Heretofore, counterbalanced rotors have been proposed. Some of theseused fixed weights arranged on the side of the driving shaft oppositethe blade. Such rotors cannot automatically compensate for the drageffects. Other rotors have used counterweights arranged at an angle tothe centerline of the rotor blade to offset drag. These rotors, by sucharrangement, introduce cyclic vibrations into the system when the rotoris operating at any other speed or angle of attack than the precisespeed and angle of attack for which the system is designed. Still otherrotors have incorporated a pair of angularly disposed weights, one beingadJustable, with an angularly hinged blade. However, with these, as theblade moves up and down in its path of movement, the counterweightsystem becomes out of alignment with the blade and a cyclic vibrationwill result. Such action also will be different for diflerent speeds andangles of attack and coning, and proper only for one designed for set ofconditions.

Therefore, it is an object of my invention to provide an improved rotorhaving balancing means operable to inhibit vibrations over a wide rangeof operating conditions for the rotor.

A further object is to arrange structure as set forth in the precedingobject upon a driving shaft so that transient vibrations will havelittle or no appreciable effect upon the aircraft.

Other objects reside in the novel arrangement of parts, and the detailsof construction of my device, and will be obvious or pointed out in thefollowing specification and claims.

In the drawing:

Fig. 1 is a diagrammatic view of an helicopter incorporating myinvention in the rotor structor;

Fig. 2 is a detail plan view of the rotor head and the counterbalancingmechanism;

Fig. 3 is an elevation of the structure shown in F18. 2;

Fig. 4 is an end view of the counterbalance mechanism with the fairingremoved and the counterweight shown in section, and

Fig. 5 is a sectional view takenalong the line 3-5 of Fig. 3.

Referring more in detail to the drawing, in Fig. 1 a helicopter It hasan engine I! driving a clutch, gear and universal Joint mechanism l4 forturning a relatively long and flexible shaft l8 to drive a single bladedrotor l3 having a counterweight mechanism 20 .attached to the rotormechanism on the side of the driveshaft l6 opposite the blade i3. Theshaft I6 may be mounted in rubber orspring vibration dampers of knowntype to absorb transverse and torsional vibrations of the rotor II. Atorque reaction rotor 22 of the single blade type, counterweighted by amass 23, is driven by the engine l2 through a shaft shown in brokenlines and gearing, not shown. The rotor 22 may have more blades, ifdesired. A control lever 24 is provided in the cockpit to position alinkage shown diagrammatically at 26 for controlling the action of themain rotor mechanism in .a manner to be described hereinafter.

In my invention, if desired, the entire rotor blade structure may bebuilt from a single piece of material having a blade portion IS, acentral portion 32 and a counterbalance portion 34. The central portion32 has a hole 36 therein, into which a universal rotor head 38 fits. Therotor head 38 has pivots 40 and 42 therein which fit into the centralportion of the blade 32 along the feathering axis thereof to providefreedom of rotation in the pitch changing direction for the rotor bladeI3. A second pair of pivots 44 and 48 fit into the head 38 and arefastened pivotally into cars 48 and 50 carried upon the uppermost end ofthe drive shaft it. With such universal structure, the rotor blade I8 isrelatively free to flap up and down with respect to the I rotor head 38in a plane perpendicular to the axis of rotation of the shaft i6, andalso to change in pitch around its longitudinal axis.

To counterweight and balance the blade la, a counterweight mechanism 20is provided. This mechanism is mounted on the blade portion 34 upon afixed bracket having an upper arm and a lower arm 62. A curved rod 66 issecured to the ends of the arms 60 and 62. A weight 63 is mounted uponthe rod 66. As will be described hereinafter, the weight can move up anddown upon the rod 66 and back and forth with respect to the centerlineof the blade structure as viewed in Figs. 2 and 4, but in a manner toremain substantially in vertical alignment with said centerline when theblade portion I8 cones upwardly and simultaneously changes pitch. Therod 66, as viewed in Fig. 3 curves about a center coincident with thepin 46 of the rotor head structure 38. As viewed in Fig. 4, the curve ofthe rod 66 is such that as. the rotor blade [3 is changed in pitch andcones upwardly (as will occur upon the application of power thereto andupon flapping of the blade I8 in flight) the weight will ride into thedotted line position, but will maintain a position that will besubstantially in vertical alignment with the longitudinal axis of theblade structure as viewed in plan during the coning operation. In otherwords, the weight 88 is arranged upon the rod 88 so as to havesubstantially the same counterweighting effect for the blade I8 for allnormal flight conditions of coning and pitching.

In addition to the counterweight mechanism 20, I have also provided acounterbalancing means for offsetting the effect of differences in dragcaused by changing the angle of attack, or pitch, upon coning upwardlyof the blade in operation. This mechanism is diagrammatically shown at Iand comprises a weight I2 which is substantially smaller in weight thanthe counterweight mechanism 20, and is mounted for movement upon a shaft18, with or against the tension of a spring I8 that abuts a retainer 11at one end and the weight I2 at its other end. Shaft 18 has its innerend rigidly mounted in drive shaft I8 and extends therefrom at rightangles to the longitudinal axis of theblade I8. A collar I6 is securedto the weight I2 and is likewise slidable upon the rod 18, A link I8 ispivotally connected to the collar I8 by a pin 80 at one of its ends andconnected to a universal connection 82 at its other end. This universalconnection 82 is carried by a link 88 which is connected to a bracket 88secured to the under side of the rotor blade by pivot pins 88 and 80, asbest shown in Fig. 5. A universal pivot bracket 98 is secured to theedge of the blade structure. In Fig. 2, this bracket 98 is shown indotted lines in a second position, and it is to be understood that thepivot bracket 88 may be secured at intermediate positions between thesetwo positions or at other positions, for purposes to be pointed outhereinafter.

A link 88 is connected to the universal pivot bracket 88 at one of itsends and to a second pivot bracket 88 at the other of its ends. Thesecond pivot bracket 88 is mounted upon a control mechanism indicated bythe reference character I00, comprising a pair of collars I02 and I 08connected together by rotatable bearing means, not shown. The collar I08is arranged to be moved up and down'and also tilted, if desired, bycontrol rods I08 and I08. The details of the control structure have notbeen shown and will not be described except that it is to be noted thatas the control rods I08 and I08 are moved together in the same directionwith respect to the rotor head 88, the total pitch, or angle of attack,of the rotor blade I8 will be changed. As the rod I08 is movedrelatively to the rod I08, the blade I8 will be pitched differently indifferent portions of its cycle.

The mechanism I0 is adapted in operation to offset and dynamicallycounterbalance the effect of drag that acts upon the rotor blade I8.When the rotor blade is turning, a centrifugal force is generated in therotor blade that acts directly outward from the hub 88. The effect ofthe counterweight mechanism 20 will be to offset this centrifugal forceby an equal and opposite centrifugal force. However, as the blade I8impinges upon the air, a drag component will act upon the rotormechanism to impress a force, parallel to the drag, upon the rotor shaftI 8. If this force is not counteracted or counterbalanced with a singlerotor blade, a cyclic oscillation will occur 4, with each revolution ofthe rotor. The mechanism I0. however, exerts a centrifugal force whichis directly opposed to this drag effect, and for a given setting of theangle of attack of the rotor blade I8 will exert a centrifugal forcecounteracting and counterbalancing this drag effect upon the rotor shaftI 8. Small vibrations that may remain are taken up by the flexibility ofthe drive shaft I8, which may be mounted in soft rubber supports orfloating bearings, and therefore not transferred to the body of thecraft.

As the angle of attach of the rotor blade is changed by shifting thecontrol rods I08 and I88 downwardly, for example, the trailing edge ofthe rotor blade I8 will be moved downwardly by the link 88 through thepivot 88. Concurrently with this action. the link 88 mounted upon thelower side of the blade will be rocked in a clockwise direction (asviewed in Fig. 5) to move the weight 12 out toward the dotted lineposition against the compression of the spring I8 which bears upon theretainer TI carried by the rod .18. Because the weight I2 is fartherfrom the center of rotation when the angle of attack of the rotor bladeI8 is increased, the centrifugal force exerted by the weight I2 in thisposition will of!- set and oppose the increased drag effect upon theshaft I8 caused by the increase in angle of attack.

In operating my device, it will be found that under different powerinputs, different atmospheric conditions encountered in flight, andgusts of wind, there will be a flapping a tion of the rotor I8. Bysuitably positioning the pivot bracket 88 to the solid line positionshown in Fig, 2, a pitch reducing movement can be provided for themechanism to cause the angle of attack to be decreased when upwardconing occurs, and the links I8 and 88 will pull the weight I2 towardthe shaft I 8. In most instances this pulling in of the weight I2 willoccur when the rotor blade is increasing in lift and hence increasingits drag. At this time an increased drag component will be acting uponthe shaft I8. However, because the weight I2 will have an initialcentrifugal force acting thereon and will, in addition thereto, have areaction force due to the moving in of the weight upon a coning upmovement, these forces may be selected to offset the increased drag byproperly selecting the weight I2, the spring I8, the associatedoperating linkage, and positioning the pivot connection 88.

It will be noted in Fig. 5 that when the weight I2 is in its outward(dotted) position and coning occurs, the pitch or the blade willdecrease as it rocks around the universal head 88 and the connection 88,and hence the path of the pivot connection 82 will be downwardly andtoward the right. This action will also tend to increase theacceleration of the weight I2 toward the shaft I 8 in cooperation withthe force of the spring I8: and the effect upon the shaft II will be areaction force equal and opposite to such acceleration.

It is obvious that as more or less automatic pitch reduction is desiredupon coning, the pivot bracket 88 can be shifted to different positions.It is also apparent that the bracket 88 mounting the link 88 could alsobe shifted to augment or subtract from the action of the link 88 uponconing of the blade I8. Furthermore, different counterweightarrangements than the specific embodiment shown could be used. 1

In the description above, separate forces due to actions of the weight12 and the counterweight 88 have been referred to. However. theseparable forces of the two can be resolved into a single component offorce that acts at an angle to each of them. Obviously, more or lessthan two weights can have a resultant eflect for accomplishing the samenet function. Hence, I wish not to be limited in my invention only tothat form shown and described but by the scope of the following claims.

I claim:

1. A rotor comprising, an elongated blade having end portions and anintermediate shank portion, one of said end portions being formed intoan airfoil, a counterweight, counterweight mounting means on the otherend portion, said means having a portion mounting said counterweightpermitting shifting of the same when said blade changes position; aflexible torque transmission shaft for turning said blade, a universalconnection between said shaft and said blade in the shank portion of theblade, a movable weight connected to said shaft at an angle to thelongitudinal axis of said blade for counteracting drag forces of saidblade upon said shaft, and manually adjustable means connecting saidblade and said weight for moving the weight and the blade simultaneouslyto automatically vary the effective combined position of counterbalanceof said counterweight and said weight.

2. A rotor blade as set forth in claim 1 wherein the mass of the weightis less than the mass of the counterweight.

3. A rotor blade as set forth in claim 1 wherein said angle issubstantially 90 from the longitudinal axis of the blade.

4. A rotor comprising, an elongated blade having end portions and anintermediate shank portion, at least one of said end portions beingformed into an airfoil, a counterweight, counter weight mounting meanson the other end portion; a torque transmission shaft for turning saidblade, a pivot connection between said shaft and said blade in the shankportion of the blade, a movable weight connected to said shaft at anangle to the longitudinal axis of said blade for counteracting dragforces of said blade upon said shaft, and means connecting said bladeand said weight for moving the weight and the blade simultaneously toautomatically vary the effective combined position of counterbalance ofsaid counterweight and said weight.

5. A rotor blade as set forth in claim 4 wherein the mass of the weightis less than the mass of the counterweight.

6. A rotor blade as set forth in claim 4 wherein said angle issubstantially 90 from the axis of the blade.

'7. A rotor comprising in combination, an elongated blade having endportions and an intermediate shank portion, one of said end portionsbeing formed into an airfoil, a counterweight, counterweight mountingmeans on the other end portion, said means having a curved portionforming a guide for mounting said counterweight upon which thecounterweight can move when said blade changes position in coning orflapping sense, a torque transmission shaft for turning said blade, saidblade being mounted for pitch changes, a coning or flapping pivotconnection between said shaft and said blade in the shank portion of theblade, a movable weight connected to said shaft at substantially a 90angle to the longitudinal axis of said blade, said weight having asmaller mass than said counterweight, and means connecting said bladeand said weight for shifting the weight when the blade changes positionto automatically vary the effective combined position of counterbalanceof said counterweight and said weight.

8. In a rotor comprising structure having a single blade portion and ashank portion operatively connected to a drive shaft, the combinationof, a counterweight for said blade portion, mounting means for saidcounterweight permitting shifting of the counterweight when the bladechanges position, a weight movably connected with said shaft, and manualmeans for controlling the position of said blade.

9. In aircraft, a drive shaft having an axis of rotation lying in aplane, mounting means connected to said shaft by a first pivotsubstantially normal to said plane and having a second pivot lyingsubstantially in said plane, a blade mounted for feathering upon saidsecond pivot and for flapping upon said first pivot, a counterweight forsaid blade, and means connected to said blade for retaining the centerof gravity of said counterweight substantially in said plane uponflapping and feathering of said blade, comprising a curved rod passingthrough the center of gravity of said counterweight, said :gynte w tbeing slidably mounted upon said 10. With an elongated single bladedcounterweighted rotor mounted upon a shaft upon pivots for pitchchanging and flapping, the combination of control means for changingpitch thereof cylindrically and totally connected to said blade so thatflapping movements will cause pitch 4 changes, a weight mounted on saidshaft and radially movable at an angle to the longitudinal axis of saidblade for counteracting drag forces of said blade upon said shaft, andoperating connections between said control means and said weight forcausing said weight to move radially to dynamically balance transientdrag forces caused by cyclic control and flapping of said blade andstatically balance changes in total pitch.

11. With an elongated single bladed counterweighted rotor mounted upon ashaft upon pivots for pitch changing and flapping, the combination ofcontrol means for cyclically changing the pitch thereof connected tosaid blade so flapping movements will cause pitch changes, a weightcarried by said shaft and adapted for radial movement at a right angleto the longitudinal axis of said blade for counteracting drag forces ofsaid blade upon said shaft, and operating connections between saidcontrol means and said weight for causing said weight to move radiallyto dynamically balance transient drag forces caused by flapping of saidblade.

12. In a rotor, in combination, a drive shaft, a single blade having ashank portion pivotally connected to said shaft for flapping and pitchchanging movements, a radially movable weight connected to said shaft atan angle to the longitudinal axis of said blade, means for automaticallymoving said weight in response to pitch changing movements of saidblade, a movable counterweight connected to said shank opposite saidblade, and means for maintaining a constant distance between saidcounterweight and said shaft during flapping movements and for retainingthe center of gravity of said counterweight in substantially the sameplane as said shaft during pitch changing movements.

13. In a helicopter rotor, a drive shaft, a single blade having a shankportion pivotally connected to said drive shaft for flapping and pitchchanging movements, 9. counterweight for said blade said unbalanced dragforces for different pitch adjustments of said blade.

14. In a helicopter rotor, a drive shaft, a single blade having a shankportion pivotally connected to said drive shaft for flapping and pitchchanging movements, a counterweight for said blade mounted on said shankportion on the opposite side of said shaft from said blade, andmechanism operative to balance the unbalanced rotational drag forcesacting on the rotor including a weight mounted on said shaft andradially movable at an angle to the longitudinal axis of said blade, andmeans operatively connecting said weight and blade for effecting radialmovement of said weight toward and away from said blade axis in responseto changes in blade pitch.

15. In a helicopter rotor, a drive shaft, a single blade having a shankportion pivotally connected to said drive shaft for flapping and pitchchanging movements. a counterweight for said blade mounted on said shankportion on the opposite side of said shaft from said blade, mechanismoperative to balance the unbalanced rotational drag forces acting on therotor including a weight mounted at one side of the longitudinal axis ofsaid blade and movable radially at an angle to said axis, manuallyoperable means for changing the pitch of said blades, and an operativeconnection between said blade and said weight for operative to balancethe unbalanced rotational I drag forces acting on the rotor including aradial shaft carried by said drive shaft and extending therefrom at anangle to the longitudinal axis of said blade, an abutment adjacent thefree end oi said radial shaft, a weight slidably mounted on said radialshaft, resilient means between said abutment and said weight for urgingthe latter toward said drive shaft, and means operatively connectingsaid weight to said blade for eflecting movement of said weight towardand from said tdlrive shaft in response to pitch changes of said ade.

MICHAEL E. GLUHAREFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,475,318.July 5, 1949.

MICHAEL E. GLUHAREFF It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 6, line 31, claim 10, for eylindrically read cyclically;

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office. Signed and sealed 22nd day of November, A. D. 1949.

THOMAS F. MURPHY,

Auiatant G'ommim'aner of Patents.

